This invention relates to reactivating partially deactivated catalysts and more particularly relates to reactivating partially deactivated catalysts based on AMS-1B crystalline borosilicate molecular sieve containing a noble metal.
Commonly assigned U.S. patent application Ser. No. 422,821 filed Sept. 24, 1982 , incorporated by reference herein, disclosed conversion of normal alkanes, such as n-butane, to more useful products such as isobutylene. The catalyst used in such conversion was based on AMS-1B crystalline borosilicate molecular sieve containing a noble metal. This catalyst, similar to essentially all heterogeneous catalysts, deactivates over time. The conventional method of reactivating such catalysts is to pass oxygen through a catalyst bed of a hydrocarbon conversion unit to burn accumulations of coke. During such oxygen regeneration hydrocarbon conversion is interrupted. A method of regenerating a catalyst without requiring a costly shutdown would be advantageous. The invention described herein is a method of onstream regeneration of a partially deactivated catalyst by addition of water. Use of small amounts of water to affect product composition in alkyl aromatic isomerization using an AMS-1B crystalline borosilicate molecular sieve catalyst was disclosed in commonly assigned U.S. patent application Ser. No. 281,730 filed July 9, 1981. However, the effect of regeneration of a partially deactivated catalyst using AMS-1B crystalline borosilicate containing a noble metal was not disclosed therein. Also commonly assigned U.S. patent applications Ser. Nos. 422,743,422,822,422,742,422,744 all filed Sept. 24, 1982 all incorporated by reference herein, disclose conversion of various alkenes under various conditions using a catalyst based on AMS-1B crystalline borosilicate.
Zeolitic materials, both natural and synthetic, are known to have catalytic capabilities for many hydrocarbon processes. Zeolitic materials typically are ordered porous crystalline aluminosilicates having a definite structure with cavities interconnected by channels. The cavities and channels throughout the crystalline material generally are uniform in size allowing selective separation of hydrocarbons. Consequently, these materials in many instances are known in the art as "molecular sieves" and are used, in addition to selective adsorptive processes, for certain catalytic properties. The catalytic properties of these materials are affected to some extent by the size of the molecules which selectively penetrate the crystal structure, presumably to contact active catalytic sites within the ordered structure of these materials.
Generally, the term "molecular sieve" includes a wide variety of both natural and synthetic positive-ion-containing crystalline zeolite materials. They generally are characterized as crystalline aluminosilicates which comprise networks of SiO.sub.4 and AlO.sub.4 tetrahedra in which silicon and aluminum atoms are cross-linked by sharing of oxygen atoms. The negative framework charge resulting from substitution of an aluminum atom for a silicon atom is balanced by positive ions, for example, alkali-metal or alkaline-earth-metal cations, ammonium ions, or hydrogen ions.
Prior art developments have resulted in formation of many synthetic zeolitic crystalline materials. Crystalline aluminosilicates are the most prevalent and, as described in the patent literature and in the published journals, are designated by letters or other convenient symbols. Examples of these materials are Zeolite A (U.S. Pat. No. 2,882,243), Zeolite X (U.S. Pat. No. 2,882,244), Zeolote Y (U.S. Pat. No. 3,130,007), Zeolite ZSM-4 (U.S. Pat. No. 3,578,723), Zeolite ZSM-5 (U.S. Pat. No. 3,702,886), Zeolite ZSM-11 (U.S. Pat. No. 3,709,979), Zeolite ZSM-12 (U.S. Pat. No. 3,832,449), Zeolite NU-1 (U.S. Pat. No. 4,060,590) and others.
Boron is not considered a replacement for aluminum or silicon in a zeolitic composition. However, recently a new crystalline borosilicate molecular sieve AMS-1 B with distinctive properties was disclosed in U.S. Pat. Nos. 4,268,420 and 4,269,813 incorporated by reference herein. According to these patents AMS-1 B can be synthesized by crystallizing a source of an oxide of silicon, an oxide of boron, an oxide of sodium and an organic template compound such as a tetra-n-propylammonium salt. The process of this invention uses AMS-1 B crystalline borosilicate molecular sieve.
Hydrocarbon conversion processes are known using othe zeolitic materials. Examples of such processes are dewaxing of oil stock (U.S. Pat. Nos. 3,852,189, 4,211,635 and Reissue No. 28,398); conversion of lower olefins (U.S. Pat. Nos. 3,965,205 and 3,960,978 and European patent application No. 31,675); aromatization of olefins and aliphatics (U.S. Pat. Nos. 3,761,389, 3,813,330, 3,827,867, 3,827,868, 3,843,740, 3,843,741 and 3,914,171); hydrocracking and oligomerization of hydrocabons (U.S. Pat. Nos. 3,753,891, 3,767,568, 3,770,614 and 4,032,432); conversion of ethane to aromatics and C.sub.3.sup.+ hydrocarbons (U.S. Pat. No. 4,100,218); conversion of straight-chain and slightly branched-chain hydrocarbons to olefins (U.S. Pat. Nos. 4,309,275 and 4,309,276); and conversion of C.sub.4 paraffins to aromatics (U.S. Pat. No. 4,291,l82).
A method to reactivate a catalyst system containing AMS-1 B crystalline borosilicate would be desirable and a method to reactivate such catalyst in a continuous manner during hydrocarbon conversion would be very advantageous.